What best describes the operation of a typical hydro block valve when an elevator is parked at the lobby?

In a typical hydro block valve system for elevators when they are parked at the lobby, the Down Valve is closed, the Check Valve is closed, and the Up Valve is open. This configuration is crucial for ensuring the safety and stability of the elevator when it is not in use.

When the elevator is parked, keeping the Down Valve closed prevents any descent of the elevator car, thereby ensuring that it remains stationary. The Check Valve's role is to prevent backflow, which adds an additional layer of safety by ensuring that hydraulic fluid cannot move back through the system, thus keeping the elevator securely in place and preventing any accidental movement.

Furthermore, the Up Valve being open allows for the system to maintain pressure, and it also prepares the elevator for immediate upward movement once an upward command is given. This setup ensures that the elevator is secure while parked and ready to operate safely when called upon.

This operation fosters a stable and reliable system that is essential for elevator functionality, focusing on safety and efficiency.